Goshen stone, a metamorphic rock derived from sandy mud sediments deposited on an ancient sea bottom some 400 million years ago, is quarried on private land in western Massachusetts. If you find it or other mineral or stone deposits, call your state geologist’s office to check it out.

When minor league baseball pitcher Matt White purchased 50 acres of forest and farmland in western Massachusetts from his great-aunt Josephine, he wasn’t looking to get rich. His aunt needed money to help pay nursing home bills and White wanted to build a house with a view of the mountains — a place to spend the off-season. But when he and his father tried to carve out a road, they ran into problems. “Every time he dug,” White says, “he’d dig up a stone.”

White is no geologist, but he found so many flat rocks on his property that he got curious. He discovered that his neighbor was quarrying the same rock and selling it for landscaping. The blue-gray schist, called Goshen stone, tends to split into slabs ideal for rock walls, flagstones and stone steps. “I had no idea how much it was worth,” White says. “I just knew it was worth something.” Last year White decided to figure out just how much. So he called Peter Panish, a geologist at the University of Massachusetts at Amherst. According to Panish’s calculations, White’s hill contained about 24 million tons of Goshen stone. At $100 per ton — not an unreasonable amount to expect — White’s mountain would be worth $2.4 billion.

Many have dreamed of finding a billion-dollar geologic jackpot in their backyard. Some have even been tricked into thinking an odd-looking rock is their ticket to riches. “What they think might be significant,” says Jim Reger of the Maryland Geological Survey, “usually turns out not to be.” Reger has worked for the survey for more than two decades, but he has yet to see someone strike literal or figurative gold. “We’ve got people that go through old industrial sites and find blast furnace slag and they bring it to us thinking it’s worth something,” Reger says. “One fella was so sure,” Reger remembers: The man brought in a piece of banded turquoise-colored glass, likely from an old industrial furnace, that was “worthless except as a paperweight.” Reger told him as much, but the man didn’t believe him. Moreover, he refused to say where he found it. “He was afraid that we were going to go out and try to steal it from him,” Reger says.

So how can you tell if you’re holding a paperweight or a truly valuable mineral? Ask for help. Your state geological survey is a good place to start. That’s how White found Panish; the state geologist referred him. “If we get requests we can’t answer, we steer them in the right direction,” Reger says. To find contact information for your local geological survey, visit: www.stategeologists.org.

Of course, rocks aren’t the only backyard bounty worth checking out. If you find a bone rather than a stone, your best bet is to contact a local university or science museum. Kenneth Carpenter, curator of vertebrate paleontology at the Denver Museum of Nature & Science, is often called on to determine whether old bones come from a dinosaur. More often than not, he says, they don’t. “For every 20 claims, there might be one that’s a genuine fossil,” he says. But sometimes the genuine one is a big deal. A man once called to report finding dinosaur bones while walking his dog. “When we got the phone call, I was real skeptical,” Carpenter recalls. So he sent a couple of seasoned volunteers to the site. The bones turned out to be a partial Tyrannosaurus rex skeleton.

Courtesy of Goshen Stone Co., Inc., Mary Gravel

Two workers examine the Goshen stone on Gary Warner’s property.

Such fossils can be valuable. A million dollars for a T-rex skeleton isn’t as far-fetched as it might seem. The most famous T-rex, Sue, was purchased by the Field Museum of Natural History in Chicago in 1997 for $8.3 million at Sotheby’s. Most fossils, however, go for far less. A single complete T-rex tooth sells on the Internet for a mere $5,000 — not enough to make a person consider early retirement.

Not all geologic treasures are from the distant past; some come from outer space. Randy Korotev at Washington University in St. Louis, Mo., has received so many meteorite identification requests over the years that he has set up a Web site to help people figure out what to do with their potential space rocks. The first step, Korotev says, is to go through the meteorite checklist (meteorites.wustl.edu/realities.htm). Then compare your rock to his pictures of actual meteorites (and “meteorwrongs”). If you’re still convinced that your rock is a meteorite, he’ll try to help you. Many natural history museums — including the Smithsonian Institution — or universities with faculty who study meteorites will provide the same service. But be prepared for disappointment — chances are your rock originated on Earth. According to The Meteoritical Society, only about 1,500 meteorites have been recovered in the United States. “Not everything that falls from the sky is a meteorite,” Korotev says on his site. “Every rock that someone has described as ‘it wasn’t there yesterday’ was just the right size for throwing.”

If you do find minerals, fossils or meteorites on your land, you’re free to do what you will with them. “It’s pretty much finders-keepers,” says Steve Simon of the University of Chicago in Illinois. You can put them on your mantle, sell them, or “donate them to the museum for a nice tax deduction,” Simon adds. The rules vary for federal- or state-owned lands, but they are generally stricter.

Billion-dollar geological finds are extremely rare. Even White, with his mountain of Goshen, isn’t likely to join the ranks of the nouveau riche. The stone is common in the area and it doesn’t just fall out of the ground; extracting it takes money and time, says Gary Warner, White’s neighbor who has been selling Goshen stone for decades. “There’s quite a science to extracting it,” Warner says. He and his workers have to dynamite the stone, dig it out and then split it into usable pieces. It’s a lengthy process, and not all the stone is usable, he adds. Warner says he is lucky if he can recover half of the rock he pulls out. Some is lost during blasting and the rest is junk. “If you sat at the bar and figured out how to make your first billion,” Warner says, “you could do it on paper, but reality is a different thing.”

For his part, White is realistic. He’s not quitting his day job: “My goal of getting to the big leagues is the same as it ever was,” he says. The quarry is just “a nice backup plan.”

Willyard is a freelance science writer currently based in New York City.